[Engine] Grey smoke

[JT1]

2011 B9 1.6 HDi 62,000

Issue: grey smoke from exhaust all the time.

Diagnosis (so far):
Otherwise runs fine, good performance, steady idle
Oil level normal - not using any nor adding to the level
No fault codes on OBD reader
No back pressure on DPF (was cleaned in October last year)
No air intake leaks
Turbo is fine

Last 3 refuels have been with Premium diesel. A bottle of Forte Diesel cleaner was added in December and again in January. Two weeks ago Forte Injector cleaner was added along with 20 litres of Premium fuel.

Has me and now the local garage foxed.
What is left to check?
Blocked air filter or fuel filter?
Compression test although oil consumption is nil between services?

The car's mileage over the last couple of years has reduced dramatically with much fewer motorway miles and more local mileage resulting in the DPF becoming blocked last year. It's been serviced annually, including oil and filter change, irrespective of mileage.

Really grateful for any ideas or suggestions as to what it may be. Thanks.

[Drummond]

Guesses from absolute diesel noobie: could it be leaking injector? I’d look at the injector correction values, although I dunno if those correlate in any way to leaking.

[JT1]

Thanks Drummond, you and me both. it's definitely worth a try so will check and see.

[shtu]

Smoke = something's burning. There's two other possibles I can think of quickly, neither of which sound massively likely,

Water. Head gasket failure, EGR cooler leak would be possibles. But you should see coolant being used.
Oil. Is the oil in good condition? Maybe the oil is being both burned and gradually diluted.

As I say, both are not very likely with the symptoms mentioned.

Air and fuel filters - a blocked air filter would probably show up a lack of power and is a 15-minute job to check\replace, a blocked fuel filter much the same, plus low fuel pressure codes. I'd expect any decent garage to have at least looked at the air filter, but easy enough.

I'd be looking at the injectors, a "bosch diesel" agent should have the kit to properly bench-test the injectors and measure them against the intended spec, there are plenty of outfits that should be able to do it - you're really looking for someone who does little else but diesel injection work. A place that reads like this, eg, http://www.pattersondiesel.com/injector-...libration/

[JT1]

Thanks shtu, second day at the local garage and several areas appear to have been ruled out.
Oil condition is ok, pitch black obviously but not thin. Not the turbo as they've had a camera in and can see the vanes rotating; the air cleaner was changed at the last service (November) and is clean as a whistle - they'd checked it as with the recent wet weather they'd had customers' cars sucking water and soaking the filter.
They've run a pretty comprehensive diagnosis and there doesn't appear to be anything obviously awry so he's going to have a think over the weekend (car isn't really useable as it's bad enough for cars following to back off - at least I don't get any tailgaters?).
Thanks too for the link for injection specialists, there's one about 8 miles away so if we're still drawing a blank on Monday, that maybe the next step. Appreciate the thought and time to comment.

[shtu]

One other easy thing to try - unplug the MAF and see if the problem goes away. They seem prone to iffy MAFs causing running issues.

[JT1]

Thanks, I'll get them to do that - I'll be a bit miffed of that clears it as it'd have saved two days worth of work, whilst at the same very relieved!

[Wightlingo]

Leaking intercooler hose perhaps.

[JT1]

Added to the list! Thanks for the reply.

[Guanock]

If it is so noticeable, then a good test is to smell the exhaust. All the various fluids that could be burning have quite different smells.

Geoff